Novel rheology regulators such as ground natural calcium carbonates optionally treated with a fatty acid or salt and their use

ABSTRACT

The invention relates to the selection of a natural calcium carbonate crushed to a high degree of fineness, possibly treated with one or more fatty acids or one or more of their salts or mixtures thereof, and its use as a rheology regulator for polymeric compositions. 
     The specific surface area is 14 to 30 m 2 /g measured according to the BET method to ISO 4652, and the oil absorption is greater than 16 measured according to ISO 787-V (Rub-out method). 
     The conditions of mixing of the constituents and manufacture are improved, as well as the properties of the final product.

This is a divisional application of U.S. application Ser. No. 11/733,408, filed Apr. 10, 2007, which is a continuation application of U.S. application Ser. No. 10/781,686, filed Feb. 20, 2004, which is a continuation of U.S. application Ser. No. 09/806,473, filed Jul. 3, 2002, which is a 371 of PCT/IB99/01625, filed Oct. 1, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the technical sector of sealants, coatings, adhesives, plastisols or rubbers.

2. Description of the Related Art

There are known, in this field, polymeric compositions, with or without fillers, for example polyurethanes with a silane termination which are used as sealants or adhesives setting in moist conditions.

In the presence of moisture, terminal silane groups undergo, in a known manner, a hydrolysis and condensation reaction. A stable siloxane lattice (Si—O—Si) then foams.

Such products have many applications in various industrial fields such as the transport and building industries.

More and more sophisticated formulations have therefore been sought, notably of the “single-component” type, capable of being applied to various substrates posing problems which are more and more difficult to resolve.

The composition of this type of formulation comprises one or more fillers, which can be one or more calcium carbonates normally referred to as “fine”.

It has been discovered according to the invention that, surprisingly, the selection of a natural calcium carbonate ground to a high degree of fineness, which will be described below, or this calcium carbonate treated also as described below, makes it possible to achieve an unequalled set of satisfactory properties for the final product. These include notably good adaptability to adhesion on many types of substrate, such as certain difficult plastics, including without a prior primer coating called “primer”, a reduction in the quantity of polymer required (and therefore a reduction in the cost of materials), or an appreciable reduction in the mixing time (which may reach a factor of ½ for each step, which has an obvious great economic advantage).

It is even more surprising to find that this remarkable improvement in a set of properties of the final product does not take place, as an expert would logically predict, to the detriment of the final mechanical properties, or properties such as resistance to chemical agents or UV radiation or similar properties conventionally required of such agents.

Formulations of the plastisol type based on polyvinyl chloride (PVC) are also known.

It should be stated here that a plastisol designates a suspension of one or more PVC resins in a liquid plasticiser and additives such as mineral fillers, stabilisers, mineral and/or organic pigments, expansion agents, adhesion promoters, fluidifiers and others.

After thermal gelling, the plastisol takes the appearance of a more or less flexible compact mass.

One of the mineral fillers normally used consists of a synthetic calcium carbonate obtained chemically (precipitated calcium carbonate: PCC) such as for example the product Winnofil SPT Premium™ from Zeneca.

According to the invention, it is proposed to use, as a rheology regulating mineral material, a natural calcium carbonate crushed to a high degree of fineness whether or not with a dispersing agent present. This natural calcium carbonate is chosen from amongst chalk, calcite or marble, alone or in a mixture, or from amongst these same calcium carbonates treated by means of at least one fatty acid or its salt or a mixture thereof and preferentially using stearic acid or its salt, such as notably calcium, magnesium or zinc stearate and highly preferably using stearic acid or its calcium salt, the whole as described in more detail below.

The rheology regulator product according to the invention is characterised in that it is a case of a natural calcium carbonate, with a specific surface area of around 14 to 30 m²/g, preferably 16 to 24 m²/g and highly preferentially around 20 m²/g, measured according to the BET method to ISO 4652.

This carbonate is possibly treated with at least one fatty acid or its salt or a mixture thereof, an acid which is an acid containing 10 to 24 atoms of carbon, and more particularly stearic acid or its salt, such as notably calcium, magnesium or zinc stearate and highly preferentially by means of stearic acid or its calcium salt, preferably at the rate of 0.01% to 5% by weight and more preferentially 1% to 4% by weight.

It should be noted here that stearic acid means stearic acids of industrial quality composed mainly of 50% to 70% octadecanoic acid and 30% to 50% hexadecanoic acid.

An original advantage of the product according to the invention is that this product is a calcium carbonate which fulfils a rheology regulating function. This function is normally devolved to the polymers and additives contained in the polymeric formulation, such as for example viscosity depressors, and the Applicant was surprised to see it fulfilled by a product of the type consisting of a material with a natural mineral filler with a high degree of fineness.

The product selected according to the invention consists of a natural calcium carbonate crushed very finely with a dispersant present or not and possibly treated by means of at least one fatty acid or its salt or a mixture thereof.

Another of its characteristics lies in its oil absorption, which is greater than 16, measured according to ISO 787-V (Rub-out method).

A calcium carbonate with a specific surface area of 19 to 26 m²/g was described in the patent EP 0 795 588. It is known according to this document as a pigment giving brightness and opacity in the papermaking field. This field of application is totally different. In addition, such a function is completely different from that of a rheology regulating action, and nothing would suggest either the function brought to light by the invention, nor the fact that this novel application could lead to a surprising set of properties having a great economic advantage.

The invention also relates to the use, as a rheology regulator for the preparation of sealants or coatings, adhesives, plastisols or rubbers, of these natural calcium carbonates crushed to a very high degree of fineness, possibly treated by means of at least one fatty acid or its salt, notably of calcium, magnesium or zinc or a mixture thereof. This acid, which is an acid containing 10 to 24 atoms of carbon, is more particularly stearic acid or its salt, such as notably calcium, magnesium or zinc stearate and highly preferentially stearic acid or its calcium salt. The processing takes place preferably at the rate of 0.01% to 5% by weight and more preferentially 1% to 4% by weight of at least one fatty acid or its salt or a mixture thereof.

The invention also relates to the use of dispersions or suspensions, in an organic medium, of these calcium carbonates, treated or non-treated, as a rheology regulator for the preparation of sealants or coatings, adhesives, plastisols or rubbers.

The invention also relates to polymeric compositions of plastisols, sealant or coating, elastomer or rubber containing, as a rheology regulator, the said natural calcium, carbonates crushed to a high degree of fineness, possibly treated by means of at least one fatty acid or its salt or a mixture thereof.

Other characteristics and advantages of the invention will be understood more clearly from a reading of the following description and examples. These examples should not be taken to represent any limitative aspect of the invention.

In the examples, the products have the following characteristics:

Product A:

A filler of the prior art, consisting of a natural calcium carbonate of the chalk type, crushed and dried, not treated, with a mean grain diameter of 0.67 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area of 11 m²/g measured according to the BET method to ISO 4652.

Product B:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the chalk type, crushed and dried, not treated, with a mean grain diameter of 0.60 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area of 19.5 m²/g measured according to the BET method to ISO 4652 and with an oil absorption of 18.75 measured according to ISO 787-V (Rub-out method).

Product C:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the Urgonian calcite type, crushed by the wet method and dried, not treated, with a mean grain diameter of 0.44 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area of 16.5 m²/g measured according to the BET method to ISO 4652 and with an oil absorption of 20 measured according to ISO 787-V (Rub-out method).

Product D:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the chalk type, crushed by the wet method and dried, treated by the use of 3% by weight stearic acid, with a mean grain diameter of 0.59 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area, after treatment, of 16 m²/g measured according to the BET method to ISO 4652 and with an oil absorption, after treatment, of 16.3 measured according to ISO 787-V (Rub-out method).

Product E:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the Urgonian calcite type, crushed by the wet method and dried, not treated, with a mean grain diameter of 0.58 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area of 14.4 m²/g measured according to the BET method to ISO 4652 and with an oil absorption of 17.9 measured according to ISO 787-V (Rub-out method).

Product F:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the chalk type, crushed by the wet method and dried, treated by the use of 1% by weight stearic acid, with a resulting granulometry of 96%<1 micrometre and 39%<0.2 micrometres measured by means of the Sedigraph 5100 from Micromeritics, with a specific surface area, after treatment, of 28 m²/g measured according to the BET method to ISO 4652 and with an oil absorption, after treatment, of 19.5 measured according to ISO 787-V (Rub-out method).

Product G:

A rheology regulator according to the invention, consisting of a natural calcium carbonate of the chalk type, crushed by the wet method and dried, not treated, with a specific surface area of 22 m²/g measured according to the BET method to ISO 4652 and an oil absorption of 19.4 measured according to ISO 787-V (Rub-out method).

Product H:

A filler of the prior art consisting of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™.

Product I:

A filler of the prior art, consisting of natural calcium carbonate of the chalk type, crushed by the wet method and dried, treated by means of 1% stearic acid, with a mean diameter of 1.4 micrometres measured by means of the Sedigraph 5100 from Micromeritics and with a specific surface area of 6 m²/g measured according to the BET method to ISO 4652.

Product J:

A filler of the prior art, consisting of a natural calcium carbonate of the chalk type, crushed by the wet method and dried, treated by the use of 1% by weight stearic acid, with a mean diameter of 1 micrometre measured by means of the Sedigrapb 5100 from Micromeritics and a specific surface area of 10 m²/g measured according to the BET method to ISO 4652.

Product K:

A filler of the prior art consisting of a treated precipitated calcium carbonate sold by Solvay under the name Socal U1S2.

EXAMPLE 1

This example relates to the use of calcium carbonate as a rheology regulator for the preparation of plastisols.

In these tests, tests were carried out on the replacement of the synthetic calcium carbonate obtained by precipitation, of the prior art, or precipitated calcium carbonate (PCC), by the specific natural calcium carbonate according to the invention.

In a formulation of the plastisol type based on PVC (polyvinyl chloride) containing no calcium carbonate, it was sought to compare the effect of the replacement of 50% to 100% of the mineral filler normally used, namely a precipitated calcium carbonate, by a natural calcium carbonate crushed to a high degree of fineness according to the invention.

To do this, with 75 g of plastisol without filler, the calcium carbonate to be tested was mixed in a 7 cm diameter receptacle and the mixture was homogenised with a spatula. Then the mixture was put in dispersion for two minutes using a “Pendraulik” ™ LD50 laboratory mixing appliance, the diameter of the dispersing disc being 5 cm, the speed of rotation of the disc being 2700 rev/min (manual setting at position 3).

The dispersing being terminated, the viscosity was measured by means of “Rheomat 120” M equipment, a measuring appliance according to DIN 125, at 20° C.

Test No. 1:

This test illustrates the prior art and uses 20 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H) and 5 g of natural calcium carbonate sold under the name Juraperle™ BS by Juraweiss.

Test No. 2:

This test illustrates the prior art and uses 13 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H) and 12 g of product A according to the prior art.

Test No. 3:

This test illustrates the invention and uses 25 g of product B according to the invention.

Test No. 4:

This test illustrates the prior art and uses 20 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H).

Test No. 5:

This test illustrates the invention and uses 10 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H) and 15 g of product D according to the invention.

Test No. 6:

This test illustrates the invention and uses 10 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H) and 15 g of product C according to the invention.

Test No. 7:

This test illustrates the invention and uses 13 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H) and 12 g of product E according to the invention.

Test No. 8:

This test illustrates the invention and uses 10 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H), 5 g of natural calcium carbonate sold under the name Juraperle™ BS by Juraweiss and 10 g of product D according to the invention.

Test No. 9:

This test illustrates the invention and uses 10 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT™ (product H), 5 g of natural calcium carbonate sold under the name Juraperle™ BS by Juraweiss and 10 g of product E according to the invention.

Test No. 10:

This test illustrates the invention and uses, for a mixture with 72 g of plastisol, 10 g of a precipitated calcium carbonate sold by Zeneca under the name Winnofil SPT (product H), 5 g of natural calcium carbonate sold under the name Juraperle™ BS by Juraweiss and 13 g of product E according to the invention.

The results of the viscosity measurements as a function of the speed of flow according to DIN 125 at 20° C. are set out in Tables Ia and Ib below.

TABLE Ia Prior Prior Inven- Prior Inven- art art tion art tion TEST N° 1 2 3 4 5 COMPO- Plastisol 75.00 75.00 75.00 75.00 75.00 SITION without filler (in g) PCC (in g) 20.00 13.00 — 25.00 10.00 Juraperle ™ 5.00 — — — — BS (in g) Product A — 12.00 — — — (in g) Product B — — 25.00 — — (in g) Product D — — — — 15.00 (in g) Weight of 100.00 100.00 100.00 100.00 100.00 mixture (in g) Viscosity mPa · s Speed of Test N° Test N° Test N° Test N° Test N° flow s −1 1 2 3 4 5 RHEOL- 20 18200 17700 15200 17600 17100 OGY 40 10040 9650 8430 9900 9650 60 7260 7100 6280 7200 7100 80 5890 5730 5170 5850 5700 100 5100 4880 4390 5000 4800 120 4490 4380 3980 4450 4350 140 4100 4020 3550 3990 3990 160 3780 3650 3310 3650 3650 180 3460 3400 3110 3400 3380 200 3320 3220 2950 3190 3170 220 3140 3030 2780 3110 3000 240 3000 2870 2620 2890 2820 260 2870 2760 2520 2740 2700 280 2760 2680 2420 2610 2600 300 2660 2570 2350 2490 2490

TABLE Ib Inven- Inven- Inven- Inven- Inven- tion tion tion tion tion Test N° 6 7 8 9 10 COMPO- Plastisol 75.00 75.00 75.00 75.00 72.00 SITION without filler (in g) PCC (in g) 10.00 13.00 10.00 10.00 10.00 Juraperle ™ — — 5.00 5.00 5.00 BS (in g) Product C 15.00 — — — — (in g) Product D — — 10.00 — — (in g) Product E — 12.00 — 10.00 13.00 (in g) Weight of 100.00 100.00 100.00 100.00 100.00 mixture (in g) Viscosity mPa · s Speed of Test N° Test N° Test N° Test N° Test N° flow s⁻¹ 6 7 8 9 10 RHEOL- 20 12700 17300 13100 12500 17000 OGY 40 7280 9450 7600 7160 9500 60 5360 6950 5630 5250 7030 80 4430 5600 4850 4330 5580 100 3820 4830 4040 3780 4800 120 3400 4230 3600 3300 4320 140 3110 3950 2290 3000 3790 160 2860 3550 3040 2770 3550 180 2680 3260 2850 2590 3280 200 2520 3110 2680 2480 3080 220 2400 2910 2550 2320 2950 240 2290 2790 2430 2200 2800 260 2190 2670 2340 2130 2710 280 2120 2580 2250 2050 2610 300 2040 2490 2180 1970 2490

A reading of the table shows that the use of the calcium carbonate according to the invention makes it possible to regulate the rheological behaviour of the plastisol composition, even when 100% of the precipitated calcium carbonate has been replaced by the calcium carbonate according to the invention.

EXAMPLE 2

This example relates to the study of the conventional mechanical properties conferred by product F according to the invention, that is to say a natural chalk crushed so as to obtain a specific surface area of 28 m²/g, on mixtures based on plasticised PVC, in comparison with mixtures filled by means of natural calcium carbonates well known in the prior art.

For each of these tests, the following mixture was produced:

“SOLVIC 239 D” PVC sold by Solvay 100 Dioctyl phthalate (Jayflex ™ DOP from Exxon) 50 Dibasic lead sulphate 1 Tribasic lead sulphate 2 Filler to be tested 80

Preparation of the Composition:

The dry mixtures or “dry blends” were prepared in a “GUEDU”™ adiabatic mixer at 100° C. for a period of 15 minutes. The mixtures were then gelled on cylinders at 150° C. in a mixing mill. For all the mixtures, this operation was performed in 12 minutes.

Sheets of 90×90×2 mm were then moulded at 160° C. after preheating of the blank for 3 minutes and pressurising for 2 minutes before cooling, using a compression press.

The test pieces necessary for determining the mechanical properties were cut from these sheets.

The different calcium carbonates tested were:

Test No. 11:

This test illustrates the prior art and uses a natural chalk, treated with 1% stearic acid, with a specific surface area of 6 m²/g measured according to the BET method to ISO 4652 (product 1).

Test No 12:

This test illustrates the prior art and uses a natural chalk, treated with 1% stearic acid, with a specific surface area of 10 m²/g measured according to the BET method to ISO 4652 (product J).

Test No. 13:

This test illustrates the invention and uses product F according to the invention.

The mechanical properties were assessed by means of dynamometric tests (tensile strength, breaking elongation, modulus 100%) carried out using the Instron™ equipment according to ISO 37, at a temperature 23° C. and with a traction speed of 10 cm/min.

The ASTM-C tear strength was for its part determined according to the method of ISO R-34 and Shore C hardness according to the method of ISO 868.

The results of these measurements of mechanical properties are set out in Table II below.

TABLE II Test No. Prior art Prior art Invention 11 12 13 Tensile strength (daN/cm²) 128 130 136 Breaking elongation (%) 300 260 172 Modulus 100% (daN/cm²) 83 106 127 ASTM-C tear strength (daN/cm) 47 56 58 Shore C hardness at 15 s (in daN/cm) 60 64 74

It can be seen that the mechanical properties obtained are excellent and are superior to those obtained with natural calcium carbonates which are crushed but which have a specific surface area outside the scope of the invention.

The invention therefore makes it possible to optimise the formulations according to the mechanical property to be favoured.

EXAMPLE 3

This example relates to the use of calcium carbonates as a rheology regulator for the preparation of elastomer based on natural or synthetic rubber.

It was sought in this example to assess the effect of the specific surface area of a crushed natural chalk according to the invention on the properties of mixtures based on natural and synthetic rubbers, in comparison with a precipitated calcium carbonate of the prior art.

To do this, for each of Tests 14 and 15, the following mixture was produced;

Natural rubber (smoked sheet quality RSS 1) 100 SBR rubber (styrene-butadiene, Cariflex ™ 1502 from Shell) 40 Zinc oxide (snow quality) from Vieille Montagne 5 Stearic acid 2 Sulphur 1.5 N-cyclohexyl 2 benzothiazyl sulphenamide (Vulcafor ™ CBS from 1 Vulnax) Tetramethylthiuram disulphide (Vulkacit ™ DTMT from Bayer) 0.5 Calcium carbonate to be tested 100

Test No. 14:

This test illustrates the prior art and uses a precipitated calcium carbonate sold by Solvay under the name Socal U1S2 (product K).

Test No. 15:

This test illustrates the invention and uses product F according to the invention.

These two tests were carried out as follows:

A pure gum master-batch was prepared, by the successive incorporation of the various ingredients, except for calcium carbonate, according to the normal technique of experts, on a mixing mill regulated for temperature, by mixing for 10 minutes (friction I/I,4) at 60° C.

From this master-batch two samples were taken in which the calcium carbonates to be tested had been incorporated, by mixing at 60° C. for 12 minutes.

After determination of the vulcanisation optima at 155° C. using a Monsanto flow meter, sheets were moulded and vulcanised to this optimum in order to effect the measurement of the mechanical properties according to the same operating method as in the previous tests.

The results of the mechanical properties are set out in Table III below.

TABLE III Test No. Prior art Invention 14 15 Vulcanisation optimum at 155° C. 5 min. 15 s 5 min. Tensile strength daN/cm² 119 109 Modulus 300% daN/cm² 41 39 Elongation % 500 485 Tear strength ASTM-C daN/cm 23 26 Shore A hardness (15 s) 61 61

It can be seen that the product according to the invention reduces the implementation time (the vulcanisation optimum) as well as the tear strength properties.

Likewise Tests 16, 17 and 18 were carried out using the following formulation:

SBR rubber (styrene-butadiene, Cariflex ™ 40 1502 from Shell) Natural rubber (smoked sheet quality RSS 1) 60 Zinc oxide (snow quality) from Vieille Montagne 5 Stearic acid 2 Sulphur 2 N-cyclohexyl 2 benzothiazyl sulphenamide 0.9 (Vulcafor ™ CBS from Vulnax) Diorthotolylguanidine accelerator (Vulkafor ™ 0.3 DOTG from Vulnax) Calcium carbonate to be tested 100

Test No. 16:

This test illustrates the prior art and uses a precipitated calcium carbonate sold by Solvay under the name Socal U1S2 (product K).

Test No. 17:

This test illustrates the prior art and uses a calcium carbonate of the chalk type, crushed by the wet method and dried, treated, with a mean diameter of 1.4 micrometres measured by means of the Sedigraph 5100 from Micromeritics and with a specific surface area of 10 m²/g measured according to the BET method to ISO 4652 (product J).

Test No. 18:

This test illustrates the invention and uses product G according to the invention.

From this master batch manufactured with the same operating method as in the previous test, three samples were taken in which the calcium carbonates to be tested had been incorporated, by mixing at 60° C. for 12 minutes.

After determination of the vulcanisation optima, sheets were moulded and vulcanised to this optimum in order to effect a measurement of the mechanical properties according to the same operating method as for the previous tests.

The results of the mechanical properties are set out in Table IV below.

TABLE IV Test No. Prior art Prior art Invention 16 17 18 Vulcanisation optimum 23 min. 30 s 16 min. 45 s 11 min. at 150° C. Tensile strength (daN/cm²) 122 132 132 Modulus 300% (daN/cm²) 16.5 20 20 Elongation % 695 715 695 ASTM-C tear strength 23 28 28 (daN/cm) Shore A hardness (15 s) 51 50 50 in (daN/cm)

It can be seen that the product according to the invention improves the implementation time (the vulcanisation optimum) and the majority of the mechanical properties.

EXAMPLE 4

A second series of tests (Tests 19 and 20) were carried out in a natural rubber 40 pcr filled with a mineral filler with the basic formula:

Natural rubber (smoked sheet quality RSS 1) 100 Coumarone resin 60/70 5.6 Rosin 3 Zinc oxide (snow quality) from Vieille Montagne 40 Stearic acid 0.5 Oil 4.3 Benzothiazyl disulphide accelerator 1 (Vulcafor ™ MBTS from Vulnax) Diphenylguanidine accelerator 0.36 (Vulcafor ™ DPG from Vulnax)

The calcium carbonates to be tested were:

Test No. 19:

A precipitated calcium carbonate (product K) for this test, which illustrates the prior art.

Test No. 20:

A natural calcium carbonate according to the invention (product G) for this test, which illustrates the invention.

The results of the mechanical properties, measured with the same operating method as for the following tests, are set out in Table V below.

TABLE V Test No. Prior art Invention 19 20 Vulcanisation optimum at 150° C. 7 min. 15 s 8 min. 15 s Tensile strength (daN/cm²) 246 246 Modulus 300% (daN/cm²) 32 31 Elongation % 710 710 Shore A hardness (15 s) in (daN/cm) 45 46.5

It can be seen that the product according to the invention makes it possible to obtain equivalent mechanical property results, even by completely replacing the precipitated calcium carbonate with a natural calcium carbonate. 

1. A method of regulating the viscosity as a function of speed of flow during the application of a plastisol to a substrate, comprising adding natural calcium carbonate, crushed to a high degree of fineness, with a specific surface area of around 14 to 30 m²/g measured according to the BET method to ISO 4652, to a plastisol, and adjusting the amount of added natural calcium carbonate in order to achieve a desired relationship between speed of flow and viscosity of the plastisol.
 2. The method of claim 1, wherein the calcium carbonate has a specific surface area of around 16 to 24 m²/g.
 3. The method of claim 1, wherein the calcium carbonate has a specific surface area of around 20 m²/g.
 4. The method of claim 1, wherein the natural calcium carbonate has a specific surface area of at least 14.4 m²/g.
 5. The method of claim 1, wherein the natural calcium carbonate has a specific surface area of at least 16 m²/g.
 6. The method of claim 1, wherein the natural calcium carbonate has a specific surface area of at least 16.5 m²/g.
 7. The method of claim 1, wherein the natural calcium carbonate has a specific surface area of no higher than 22 m²/g.
 8. The method of claim 1, wherein the natural calcium carbonate has a specific surface area of no higher than 28 m²/g.
 9. The method of claim 1, wherein the natural calcium carbonate is treated with at least one fatty acid containing 10 to 24 carbon atoms or a salt thereof selected from the group consisting of calcium salt, magnesium salt, zinc salt, and mixtures thereof.
 10. The method of claim 1, wherein the natural calcium carbonate is treated with stearic acid or a calcium salt thereof in a proportion of around 0.01% to 5% by weight.
 11. The method of claim 1, wherein the natural calcium carbonate is treated with stearic acid or a calcium salt thereof in a proportion of around 1% to 4% by weight.
 12. The method of claim 1, wherein the natural calcium carbonate has an oil absorption which is greater than 16 g/100 g measured according to ISO 787-V (Rub-out method).
 13. The method of claim 1, wherein the plastisol is PVC-based.
 14. A method of regulating the rheology during the application of a plastisol to a substrate, comprising adding natural calcium carbonate, crushed to a high degree of fineness, with a specific surface area of around 14 to 19.5 m²/g measured according to the BET method to ISO 4652, to a plastisol, in an amount to regulate the rheology of the plastisol.
 15. The method of claim 14, wherein the natural calcium carbonate has a specific surface area no higher than 16.5 m²/g.
 16. The method of claim 14, wherein the natural calcium carbonate has an oil absorption which is greater than 16 g/100 g measured according to ISO 787-V (Rub-out method).
 17. The method of claim 14, wherein the plastisol is PVC-based. 